Komatsu 930E-2, Shop Manual

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COMPONENT DESCRIPTION
HYDRAULIC TANK
The hydraulic tank supplies hydraulic oil for the hoist,
steering and brake circuits. The tank is located on the
left hand frame rail forward of the rear wheels. The
service capacity of the tank is 250 gal. (947 l). Type
C-4 hydraulic oil is recommended for use in the hy-
draulic system. Oil used in the hoist circuit flows
through 100 mesh wire suction strainers to the inlet
hoses of the pump. Air drawn into the tank during
operation is filtered by air filters located on the top of
the tank. Oil level can be checked visually at sight
glasses located on the face of the tank.
HYDRAULIC PUMP
The hoist system hydraulic pump is a tandem, gear
type pump driven by a drive shaft on the end of the
traction alternator. The pump has a total output of 246
GPM (931 l/m) at 1900 RPM and 2500 psi (17, 235
kPa).
A smaller, piston type, pressure compensated pump
rated at 66 GPM (250 l/m) @ 1900 RPM, coupled to
the hoist pump, supplies oil to the steering system and
brake apply system.
Hoist pressure is limited to 2500 psi (17,235 kPa) by
internal relief valves located in the hoist control valve
inlet sections.
HIGH PRESSURE FILTERS
Hoist pump output oil is directed to the high pressure
filters, mounted on the inboard side of the fuel tank.
The filter assemblies are equipped with a bypass valve
which permits oil flow if the filter element becomes
excessively restricted.
Flow restriction through the filter element is sensed by
an indicator switch. This switch will turn on a cab
mounted red warning light to indicate filter service is
required. The indicator light will illuminate when restric-
tion reaches approximately 40 psi (276 kPa). Actual
filter bypass will result when the filter element restric-
tion reaches approximately 50 psi (345 kPa).
HOIST VALVE
The hoist valve (Figure 7-2) is mounted on a modular
assembly containing the hoist valve, overcenter mani-
fold, and both hydraulic pumps. This assembly is
bolted to brackets attached to the frame rails behind
the main alternator.
The hoist valve is a split spool design. (The term “split
spool” describes the spool section of the valve.) The
hoist valve precisely follows differential pressure input
signals generated by the hoist pilot valve as the opera-
tor moves the hoist control lever while raising and
lowering the dump body.
Inlet Sections
Each of the front and rear inlet sections of the hoist
valve contains of the following components:
•
Flow control valve and main relief valve
•
Secondary Low pressure relief valve
•
Anti-void check valve
•
Load check valve
The flow control portion of the flow control and main
relief valves allow pump flow to the service brake
cooling circuit unless the body is being raised or low-
ered. The relief portion of the valve is direct acting and
has the capacity to limit the working pressure at full
pump flow.
FIGURE 7-2. HOIST VALVE
1. Inlet Section
2. Work Ports Spool
Section
3. Tank Ports Spool Section
5. Inlet Port
6. Outlet Port
7. Spool Section Cover
8. Separator Plate
L7-2 Hoist Circuit L07023